6 Jan
2022
6 Jan
'22
7:11 a.m.
-----Original Message-----
From: Jonathan Chapman <lists at glitchwrks.com>
Sent: 06 January 2022 13:00
To: rob at jarratt.me.uk; Rob Jarratt <robert.jarratt at ntlworld.com>; General
Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
Subject: RE: Source for replacement caps in H744 regulators
I was testing with a 1R resistor, so drawing 5A of the rated 25A. The other two H744s did
not whine, but this one does. I can try a bigger load, I think the best I may be able to
do is 10A, possibly 20A.
One of the H744 regulators whines
FWIW, none of mine are silent under load. If they're not being loaded (e.g.
on a test bench, with no dummy load, or if you have all the boards out) they
can whine excessively due to no minimum load. it seems higher than the expected values printed
on the meter
Beware cheap test equipment. $client has a few of these Chinese handheld
LC/RLC meters, they're wildly inaccurate on some parameters, including ESR
on large electrolytics. We've got a proper Gen-Rad RLC Digibridge in the shop
to compare against. We couldn't figure out why some of their tuned filter
stages were failing QC at a much higher rate than expected. They were off-
frequency because the cheap meters were giving consistently incorrect
measurements when trying to match capacitors.
That said, it's not like replacing them with new
will *hurt* -- it just might not
fix the whine.
Thanks,
Jonathan